Question

Моторная лодка шла по течению реки 4ч со скоростью 15км/ч.на обратный путь она затратила на 2ч больше времени. какова скорость лодки против течения? решите пожалуста

Answer 1

1) 4*15=60 путь который проехал
2)4+2=6 часов
3)60/6=10 км/ч

Answer 2

4 *15=60 км
4+2=6ч
60/6=10 км/ч

Answer 3

Problem Analysis

To solve this problem, we can use the formula:

speed = distance / time

We know the boat's speed downstream is 15 km/h, and we need to find the speed of the boat against the current.

Let's denote the speed of the boat in still water as b and the speed of the current as c.

When the boat goes downstream, its effective speed is b + c. When it goes upstream, its effective speed is b - c.

We also know that the time taken for the upstream journey is 2 hours longer than the time taken for the downstream journey.

Solution

Let's use the given information to form equations and solve for the speed of the boat in still water.

1. Downstream Journey: - Speed of the boat + speed of the current = 15 km/h - b + c = 15 2. Upstream Journey: - Speed of the boat - speed of the current = ? - Time taken = 4 hours + 2 hours = 6 hours - Distance = 15 km/h * 6 h = 90 km - b - c = 90 / 6 = 15 Adding the two equations: - b + c + b - c = 15 + 15 - 2b = 30 - b = 15 km/h

So, the speed of the boat in still water is 15 km/h.

Therefore, the speed of the boat against the current is also 15 km/h.